Norovirus, a Calicivirus (family Caliciviridae), is colloquially known as “stomach flu” or “food poisoning”. Norovirus is recognized as one of the major causes of nonbacterial outbreaks worldwide. This accounts for an estimated of 23 million infections per year in the US (the second highest cause of nonbacterial gastroenteritis (GE) morbidity) and imposes a substantial burden on healthcare.
Norovirus is classified as “NIAID category B Priority bio-defense Pathogen”. It is a non-enveloped, single-stranded, positive sense RNA genome which is environmentally stable due to capsid formation. It can resist freezing and heating to up to 60 C and is stable at low concentrations of chlorine. An infectious dose of 10-100 viruses via fecal-oral transmission or droplet transmission can lead to infection. This is a highly contagious but short-lived illness (48 hrs) causes vomiting, stomach pain and diarrhea. Also, it can cause chronic infections in transplant recipient.
Of the five geno-groups of Norovirus, GI, GII, and GIV are known to infect humans. There is no available vaccine for human Norovirus infection, with progress being hampered by the absence of suitable animal model/cell culture for preclinical testing of the candidate vaccine. Presently, the detection of viral RNA is limited to RT-PCR in the stool samples of affected humans.